A recent meta-analysis published in Review of Educational Research examined the effects of co-teaching. Co-teaching and related collaborative teaching models are defined as interventions delivered by two or more teachers or professionals in the same physical space. The authors included randomized and quasi-experimental studies that investigated the effects of collaborative teaching models on student outcomes in arts, social science, and STEM subjects in K-12, published between 1984 and 2020. After excluding studies that did not meet the criteria, as well as another 52 studies for low methodological quality, 76 studies were included in the review.
The mean effect size across the studies was +0.11, with a large variability. Characteristics highlighted in the literature as relevant factors (e.g., duration, teacher training) for the impact of co-teaching did not play a role in the results. Similar results were found for interventions conducted by trained teachers and by teaching assistants without a qualification, suggesting that co-teaching may be implemented in a more cost-effective way.
Source: Vembye, M. H., Weiss, F., & Hamilton Bhat, B. (2024). The effects of co-teaching and related collaborative models of instruction on student achievement: A systematic review and meta-analysis. Review of Educational Research, 94(3), 376–422. https://doi.org/10.3102/00346543231186588